Any history of late Assyrian art must be concerned primarily
with relief carving. Some statues in the round have been found, but the comparative
ineptitude of the majority of them suggests that this form of expression did
not come naturally to Assyrian sculptors. Portal sculptures, which many would
consider the most characteristic Assyrian art form, are not statues in the round
but "double-aspect" reliefs (that is, they are meant to be seen from either
the front or the side), apparently derived from a Hittite invention of the 14th
century BC. These impressive guardian figures--usually human-headed bulls or
lions--decorate the arched gateways and are sometimes supplemented by others
set at right angles on the adjoining facades, their heads facing sideways. Each
is composed from a single block of stone weighing up to 30 tons, roughly shaped
in the quarry and then carved in situ.

The earliest slabs, from the 9th-century palaces of Ashurnasirpal
II and his son Shalmaneser III at Nimrud, are about two metres high,
with the design arranged in two superimposed registers separated by a band of
cuneiform inscription. In those from later buildings, such as Sargon
II's palace at Khorsabad, the individual sculptured figures reach a
height of nine feet. The subjects of the designs on these reliefs are rarely
related in any way to religion. Superstitious symbols do occasionally appear
in the form of benevolent winged beings, or genies, but the primary purpose
of the picture is the glorification of the king himself, either by scenes of
ceremonial homage or by extended pictorial narratives of his achievements.

The most popular theme, giving rise to numerous variations,
involves detailed scenes of military conquest and the ruthless suppression of
revolt. These are often arranged episodically to represent successive events
in the progress of a single campaign: the Assyrian army prepares for war; led
by the king, it crosses difficult country on the way to attack a walled city;
the city is taken, burnt, and demolished; the enemy leaders are punished with
conspicuous brutality; and, finally, the victory is celebrated. Scenes such
as these are distinguished above all by their stylistic vitality and fanciful
detail. Animals as well as men are carefully observed and beautifully drawn.
The principles of perspective as later defined by the Greeks are unknown, but
attention is given to the relationship of figures in space and to devices for
suggesting comparative distance.

In the 7th-century palaces of Sennacherib and Ashurbanipal
at Nineveh, the reliefs suggest a reaction in favour of narrative
and violent activity. The slabs are covered to their full height by complicated
battle scenes in which the progress of the fighting is suggested by episodic
repetition. Types of landscape are depicted schematically, and significant episodes
or individuals are identified by a short inscription, without impairing the
overall rhythm of the design. In the intervals between their military campaigns,
Assyrian kings appear to have been much preoccupied with hunting, and scenes
from the chase provided an alternative subject for the reliefs. Lions hunted
with spears from a light chariot and herds of wild asses (onagers) or gazelles
are subjects that stimulated the imagination and sensibility of the Assyrian
artist. A contrast to these descriptive carvings is provided by the formal monumentality
of the Assyrian rock reliefs, secular or religious devices carved on vertical
rock faces in localities such as Bavian and Maltai to commemorate historical
events that took place there.